1. Field of Invention
The present disclosure of invention relates to liquid crystal displays (LCD's). More particularly, the present disclosure relates to a liquid crystal display capable of achieving a wide viewing angle.
2. Description of Related Technology
In recent times, in order to improve over a narrow viewing angle of conventional liquid crystal display devices, various driving methods for the liquid crystal display device have been developed, including a patterned vertical alignment (PVA) mode, a multi-domain vertical alignment (MVA) mode, and a super-patterned vertical alignment (S-PVA) mode.
An LCD device using the S-PVA mode typically includes pixel areas each having two sub-pixels, and each of the two sub-pixels includes a main pixel electrode and a sub pixel electrode to which different voltages are applied in order to form liquid crystal domains having different grays from each other in the pixel area. Since human viewers watching the S-PVA mode LCD device perceive an phantom intermediate value of the two gray-scales being present between the main pixel electrode and the sub pixel electrode, the S-PVA mode LCD device helps to prevent or reduce deterioration of a side visibility aspect of the displayed image due to distortion of a gamma curve under an intermediate gray scale, thereby improving the side visibility of the S-PVA mode LCD device.
The S-PVA mode LCD devices may be classified into a coupling capacitor type (CC-type) and a two-transistor type (TT-type) according to the driving method thereof.
The CC-type S-PVA mode LCD device further includes a coupling capacitor inserted between the main pixel electrode and the sub pixel electrode. This coupling capacitor drops a voltage level of a main data voltage applied to the main pixel electrode to thereby apply the dropped data voltage to the sub pixel electrode as a sub pixel voltage having a lower voltage level than that of the main pixel voltage.
The TT-type S-PVA mode LCD device applies the main pixel voltage and the sub pixel voltage having different voltage levels to the main pixel electrode and the sub pixel electrode, respectively, using two separate thin film transistors.
In comparison with the TT-type S-PVA mode LCD device, the CC-type S-PVA mode LCD device has disadvantages, such as deterioration in brightness and relatively poor side visibility. On the other hand, the TT-type S-PVA mode LCD device has better brightness characteristics and side visibility than the conventional CC-type S-PVA mode LCD device. However, since two transistors are required in the TT-type S-PVA mode, its manufacturing cost increases substantially, and it is difficult to adopt the TT-type S-PVA mode to a high-speed driving method because the number of TFT's that must be individually controlled by separate gate control signals is double that present in a CC-type S-PVA mode LCD device.
Meanwhile, in case of a storage swing method in which a wide viewing angle is achieved by changing a voltage applied to a storage electrode that is overlapped with a pixel electrode, brightness and side visibility characteristics are superior, and a manufacturing cost is low. In the storage swing method, brightness and side visibility characteristics are improved as a voltage variation increases; however, transmittance in a black brightness range undesirably increases and thus causes a drastic decrease in a contrast ratio when the voltage variation of the storage electrode is increased.